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The XAS beamline team welcomes any specific feedback you might have on these guidelines so that we can make them more accurate and usable for the XAS user community.
Proposals for Merit Access to beamtime at the Australian Synchrotron undergo two reviews:
peer review by external scientific reviewers, ranked according to criteria outlined here,
technical feasibility review by beamline staff on a pass/fail basis.
This page provides guidelines to help users in developing technically feasible proposals for beamtime at the XAS beamline.
The XAS beamline receives a large number of proposals each round, making each proposal round very competitive as many groups compete for a finite amount of time on the beamline. This results in a large number of proposals for the beamline team to review for technical feasibility (i.e. whether the experiment is fit for merit time on the beamline.). To make the process more streamlined, please read the following guide closely.
What is ‘technically infeasible’?
Technically infeasible experiments are experiments where the proposals have not shown they meet the minimum requirements for merit time on the beamline. Some examples of technical infeasibility include (but are not limited to):
The proposed experiment cannot safely be performed at XAS.
The proposal was submitted to the wrong beamline accidentally.
There is no sample table included
Submitting to the correct beamline
Every round, the XAS beamline team marks perfectly good proposals as infeasible because they were submitted to the wrong beamline. To avoid this, the spectroscopy team have created this easy to follow flowchart that outlines when you would use each beamline.
The Proposed Experiment section
The Proposed Experiment section is the place for you to describe the activities and measurements you intend to perform at the beamline. It comprises two equally important, necessary sections: the Text and the Sample Table (see next section). The proposed experiment section is not an extension of the ‘Scientific Purpose’ or ‘National Benefit’ sections.
The Proposed Experiment Text
The text of the Proposed Experiment section should give the reviewers and beamline team a sense of the experiment you intend to perform during your beamtime. The text, combined with the information presented in the Sample Table should demonstrate to the reviewers and beamline team that you have considered how best to prepare your samples for measurement, and have planned to use your beamtime efficiently. The text of the Proposed Experiment section should comprise several paragraphs describing your intended measurements, including information on the nature of the samples you will be measuring, how they will be presented to the beam, the edges you intend to measure, etc.
A brief description of your samples.
Description of the samples should be restricted to information that is relevant to the measurements and other activities performed on-site. For instance, the Proposed Experiment section is not the place for a description of how you synthesised your sample material, although you should describe the form of the sample when it is presented to the beam. If you are modifying your material for measurement, e.g. homogenisation by grinding, diluting with cellulose or boron nitride, pressing into a pellet you should detail that in the experiment section. If you are preparing your samples on-site in the chemistry lab, mention that in this section.
If you are presenting your samples undiluted you can detail how you know the abundance of the element of interest, e.g. previous bulk analysis by XRF or ICP-MS, quantification via EPMA or SEM EDS.
A justification of the energy range of your scans
If you are planning on measuring particular samples as model compounds for linear combination fitting, you can explicitly mention that in this section, as it will help the reviewers assess if they are appropriate for your unknowns.
The composition of the sample beyond the element of interest
This is important information, as the other elements present in the sample may have edges or fluorescence lines that interfere with the element of interest. It is important that you consider possible interference from other elements when designing your experiment. If you are aware of the presence of interfering elements in your samples, use this section to describe how you will mitigate the interference.
For Example:
Measuring fluorescence mode EXAFS of 5 ppm Co in soil with 30 wt% Fe2O3 is unlikely to produce publishable-quality results. This due to the overwhelming fluorescence from the Fe K emission lines.
Similarly, it is not possible to measure Ni K-edge (8333 eV) EXAFS to k=16 in a Ni-Gd alloy as the Gd L1 edge (8376 eV) will contaminate the Ni EXAFS.
If you do not know the composition of your samples, use this section to describe the strategy you will employ to measure samples of the appropriate concentration for x-ray absorption spectroscopy using your chosen analysis mode.
This could include evaluations of the data quality and repreparation of the samples in response to data quality.
If you are unable to homogenise your sample (e.g. grinding will destroy fundamental features of your sample), use this section to describe how the form of the sample may impact the quality of data you will collect (e.g. pinholes, grain size much greater than 1 absorption length) and any mitigation strategies you propose to employ.
If you know your samples will exhibit significant over-absorption (a.k.a self-absorption), detail the methods you will use to correct over absorption, e.g. correlation with transmission, correction algorithms.
If you are intending to perform radiation hardness/beam damage testing, detail your approach in this section.
If you think your samples may possess characteristics that will make measurement difficult, but are unsure how to proceed, contact the beamline team for advice.
Example Proposed Experiment Text
We propose to record Lu L3-edge XANES spectra of 34 samples of Na2O-B2O3-SiO2 glass doped with ~2000 ppm Lu. To determine the relationship between oxygen fugacity and Lu speciation, we have synthesised the glasses over 16 log units of oxygen fugacity at a constant temperature of 1400 ˚C, predicted to cover the entire Lu3+ to Lu4+ transition. The samples comprise glass beads cast in 13 mm discs, that have been sectioned and polished. The Lu content of all samples has been confirmed via LA-ICP-MS. A Lu content of ~2000 ppm is sufficiently low to avoid over-absorption effects. Samples will be presented to the beam for fluorescence mode measurement in the fluorescence RT box (FRT) a custom 3d-printed sample holder designed with input from beamline staff and employed in previous MEX1 experiments.
As reference materials we will prepare Lu2O3, LuO2, Lu2Si3O9, LuPO4 as 13 mm pellets, diluted with cellulose to a nominal Lu concentration of 2000 ppm.
All samples and reference materials will be prepared off-site at our home institution and brought to site as either polished mounts or pellets sealed into MEX standard sample holders using kapton tape.
Beam induced changes in Lu oxidation state will be investigated by monitoring the Lu3+ white line as a function of time on a previously unexposed portion of a sample.
For Experiments that use or produce hazardous gases
If your experiment will produce hazardous gases, please explain how this will be handled (eg. collect in a bag), and the potential amount in our experimental hutch (40 m3), e.g:
For in situ experiments
All in situ experiments must include a schematic or clear pictures of the cell you intend to use.In situ proposals that do not include this cannot be reasonably assessed for their technical feasibility and will therefore be marked infeasible. Additionally, it is helpful if you describe whether your group has successfully used this cell at XAS in the past.
If you require gases to run your in situ experiment, please list all required gases as well as any product gases in table format, e.g:
The Sample Table
The Proposed Experiment section must include a Sample Table conforming to the instructions presented here.
The Sample Table that outlines how you plan to allocate your beamtime is not the same as the sample spreadsheet used to assess the hazards of your samples.
Proposals submitted without a Sample Table will be marked technically infeasible.
The sample table is the heart of the Proposed Experiment section of the proposal. The importance of the sample table is that it avoids repetitive text by efficiently condensing all the following information into common format. Below are the column headings for the sample table and some more information about these columns.
Example sample table.
For more details on each column, click the column heading. An empty, editable sample table can be found here -
Note: The following sample table is an example and outlines the minimum core information required for a sample table. Sample tables that are formatted differently, contain extra information etc. may be feasible so long as they, at a minimum, contain the information listed below.
In this column each row represents a specific object, or group of similar objects that will be presented to the x-ray beam for measurement. For example, rows of the table could represent (but certainly not limited to):
a pressed pellet of a model compound;
an aliquot of solution;
a series pellets where the treatment of the sample has been varied systematically;
ex-situ electrodes representing various states of charge or a range of charge-discharge cycles;
a series of liquids that form a concentration series;
soil samples collected from a range of locations;
Avoid using discipline specific acronyms in the description of your sample unless you have defined them previously in the text of the Proposed Experiment section. Whilst everyone in your particular scientific sub-discipline might know what the acronyms mean, you cannot assume all reviewers or the beamline team will know.
Edge
The element and absorption edge you wish to investigate.
Can be either in the cryostat or at room temperature
T (transmission)
Can be either in the cryostat or at room temperature
The measurement mode dictates what information you will report in the concentration column.
You can use both modes during an experiment. You can even measure both transmission and fluorescence at the same time if your sample is suitable.
Concentration
This column, called "concentration" for brevity, reports parameters related to the composition of your sample that help communicate its suitability for the chosen analysis mode
The parameters presented in the “concentration” column of sample table depends on the analysis mode you wish you use. Note that only permissible concentration units are those listed below:
Fluorescence - express the concentration of the element of interest in the sample as presented to the beam in one of the following units:
weight percent
part per million (ppm) by weight
millimolar (liquid samples only)
NOTE: It is important that this column reports the concentration of the sample as presented to the beam, i.e. the concentration after any dilution
Samples measured in fluorescence are susceptible to over-absorption (also referred to as self-absorption). Good fluorescence samples have 2000 ppm or less of the element of interest. If your samples have weight percent abundance, you will have to dilute them, or develop a strategy for correcting for over-absorption. This strategy should be discussed in the text of the proposed experiment section.
Transmission
Edge step (Δμd) and total absorption (μTd). It is insufficient to report only one of the two.
NOTE: It is vital you understand the composition of your sample, and the properties that make a good transmission sample. See this comprehensive guide for how to calculate the appropriate dilution for transmission samples in pellet form.
The concentration you report is the concentration of the sample as presented for analysis. If you are diluting your sample for analysis, report the concentration after dilution, not the concentration of the element in the material prior to dilution.
Information in the concentration column is some of the most important information for assessing technical feasibility. Ensure the concentration reported in the table is in the appropriate units appropriate to the analysis mode.
Transmission samples must report edge step (Δμd) and total absorption (μTd).
Fluorescence samples must report concentration of the element of interest in wt%, ppm or mMol
Simultaneous fluorescence and transmission samples must report concentration relevant to both analysis modes, i.e. edge step (Δμd) and total absorption (μTd) AND concentration of the element of interest in wt%, ppm or mMol
k Max
This column reports the energy of the end of your scan expressed in wavenumber, k. If you are only interested in collecting XANES data, it is sufficient to report “XANES only”.
The definition of wavenumber can be found here, and a table of conversions between electron volts (eV) above the edge and wavenumber is provided below. e.g. a scan of the Cu K-edge to kmax = 20 would result in a maximum energy of 10503 eV (8979 eV + 1524 eV; where the energy of the Cu K-edge is 8979 eV). This value is helpful for the beamline team to assess your time estimates, and check if you will experience contamination of your EXAFS by the absorption edge of another element in your sample.
If you wish to know more about converting between k and eV you can find that information here.
Environment
The sample environment you wish to use
RT (room temperature)
In situ
Cryo (top loading cryostat).
Capillary Heater
You can employ multiple sample environments in the same experiment. There will be some time consumed to change between them.
Required Gases
List any gases you require to conduct your experiment (e.g. oxygen, argon)
Scans
The number of scans you wish to perform per sample.
If your row represents a collection of similar samples, you can represent this as number of samples x number of scans = total scans; i.e. if you have a concentration series of 10 samples, each of which you would like to perform 3 repeats, you would enter 10 x 3 = 30.
Time/Scan (hrs).
The duration of a single scan in hours.
On XAS our scans are quite fast. The number of steps, the step size, and the k max will all impact the length of a scan.
XANES only scans can be as fast as 3 minutes (0.05 hrs), while a very fine EXAFS scan to k = 20 could take 15 minutes (0.25 hrs).
If you are not sure of your scan parameters, you can find some information on choosing scan parameters here.
When expressing these times in the sample table, it is easiest to express them in hours for further calculations on time required, however, it is also acceptable to report them in minutes so long as you include the time unit. (e.g. '3 minutes' is fine but writing '3' will imply 3 hours by default.)
Total
The sum of the duration of a single scan, multiplied by any repeats.
Other Activities
Use this row to add time dedicated to activities
Beamline setup (the beamline team recommends 4-6 hours as a good estimate).
Radiation hardness/beam damage testing testing
Switching between Cryo and RT.
Cryostat sample changes (Allow 30 minutes per sample change).
Switching between ex situ and in situ.
If you add a row for radiation hardness/beam damage testing, be sure to describe your method in the text of the Proposed Experiment section
Total Time Requested
The sum of the total time for each sample, plus the times for other activities.
Beamtime is awarded in 24 hour blocks, and there are three 8-hour shifts per 24 hours. Report total time requested in hours, and the number of shifts in brackets, rounded to the nearest 3 shifts:
